Protein Complexes Containing EnaVASP Proteins 21 Listeria

The facultative intracellular pathogen Listeria monocytogenes can invade mammalian cells and once in the cytoplasm can use the host actin cytoskeleton to propel itself forward (Frischknecht and Way 2001; Gouin et al. 2005). When it reaches the plasma membrane, it can push into a neighbouring cell, thereby enabling cell-to-cell spread of this pathogen. The recruitment of host Ena/VASP proteins by FP4 motifs of the surface protein ActA is required for intracellular motility of Listeria. This uncovered for the first time the fact that Ena/VASP proteins are essential for the regulation of actin polymerisation (Chakraborty et al. 1995; Smith et al. 1996). Importantly, ActA can also bind to and activate the Arp2/3 complex. The activation of this seven-protein complex leads to the nucleation of new actin filaments from the sides of existing filaments, resulting in the formation of a dendritic array of actin filaments. The combination of the function of the Arp2/3 complex and Ena/VASP results in the formation of an F-actin tail that propels Listeria through the host cell cytoplasm (Frischknecht and Way 2001; Gouin et al. 2005).

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